A Reconnaissance Survey of the Landscapes, Soils and Vegetation of the Eastern Communal Areas (Otjiozondjupa and Omaheke Regions), Namibia Ben J. Strohbach, Marianne Strohbach, Josaphat T. Kutuahuripa and Heiner D. Mouton National Botanical Research Institute and Agro-Ecological Survey Programme Directorate Agriculture Research and Training Ministry of Agriculture, Water and Rural Development P/Bag 13184 Windhoek September 2004 In collaboration with the Desert Research Foundation of Namibia, with funding from the Global Environment Facility through the Desert Margins Program DESERT MARGINS PROGRAM 1 Table of Contents 1 Abstract ................................................................................................................. 4 2 Introduction............................................................................................................ 5 2.1 The physical environment........................................................................................ 7 2.1.1 Climate.............................................................................................................. 7 2.1.2 Geology ............................................................................................................. 8 2.1.3 Agro-ecological Zones......................................................................................... 9 3 Soil and Landscape Surveys................................................................................... 11 3.1 Preparatory Work.................................................................................................. 11 3.2 Fieldwork.............................................................................................................. 11 3.3 Laboratory Methods .............................................................................................. 11 3.3.1 Sample Preparation .......................................................................................... 11 3.3.2 Particle Size Analysis by the Rowell Auto pipette Method .................................... 11 3.3.3 Bulk Density..................................................................................................... 12 3.3.4 pH of Soil in Water (pHw), 1 M Potassium Chloride (pKCL) and pH of the Saturation Extract ...................................................................................................... 12 3.3.5 Electrical Conductivity (EC) in a Saturated Paste or 2: 5 Water: Soil Extract ......... 12 3.3.6 Cation Exchange Capacity (CEC) and Exchangeable Bases .................................. 12 3.3.7 Analysis using Spectral Atomic Absorption (SOP) ................................................ 13 3.3.8 Organic Carbon (Colorimetric Walkey-Black Method) .......................................... 13 3.3.9 Available Phosphorus in Soil (Olsen Method)...................................................... 13 3.4 Determination of Land Mapping Units and Soil Types .............................................. 13 4 Landscapes and Soils of the Eastern Communal Areas............................................. 14 4.1 Land Mapping Units .............................................................................................. 14 4.1.1 Land Mapping Unit A: Interdunal depressions (IDp) ........................................... 14 4.1.2 Land Mapping Unit B: High Kalahari sand dunes (Longitudinal dunes), sand ridges and low dunes........................................................................................... 14 4.1.3 Land Mapping Unit C: Kalahari sand plains or sand deposit (KSd)........................ 14 4.1.4 Land Mapping Unit D: Flat calcrete plains with pans (KFp) .................................. 15 4.1.5 Land Mapping Unit E: Drainages or omiramba (KOm) ......................................... 15 4.1.6 Land Mapping Unit F: Kalahari sand plains with shallow underlying calcrete (KSp) 15 4.1.7 Land Mapping Unit G: Floodplains and areas subjected to regular flooding (KFu) . 15 4.1.8 Land Mapping Unit H: Plateaux with Karstveld or limestone (CKh)....................... 16 4.1.9 Land Mapping Unit I: Eroded surface of the Plateaux (EDr)................................. 16 4.2 Soil Mapping Units ................................................................................................ 16 4.2.1 Soils of the Interdunal depressions / streets and pans ........................................ 16 4.2.2 Soils of the longitudinal dunes........................................................................... 19 4.2.3 Soils of the Kalahari sand plains and sand ridges................................................ 21 4.2.4 Soils of the calcrete plains and sand plains overlying calcrete at shallow depth .... 21 4.2.5 Soils of the omiramba or drainage lines ............................................................. 22 4.2.6 Soils of the areas subject to flooding ................................................................. 25 4.2.7 Soils of the Karstveld and ridges........................................................................ 26 5 Phytosociological classification of the vegetation ..................................................... 27 5.1 Methods ............................................................................................................... 27 5.1.1 Initial stratification ........................................................................................... 27 5.1.2 Field surveys.................................................................................................... 28 5.1.3 Data basing, -clean up and archiving procedures................................................ 29 5.1.4 Vegetation Data processing............................................................................... 29 5.2 Results and discussion........................................................................................... 29 5.2.1 Taxonomic overview of the species recorded during the survey........................... 29 1 5.2.2 Phytosociological analyses ................................................................................ 30 6 The Terminalia - Combretum Savannas .................................................................. 34 6.1 The Pterocarpus angolensis - Burkea africana tall, moderately closed bushland association ........................................................................................................... 34 6.2 The Terminalia sericea - Combretum collinum moderately closed shrub- and bushland association ........................................................................................................... 37 6.2.1 The Terminalia sericea - Schinziophyton rautanenii tall, moderately closed bushland subassociation ........................................................................................... 37 6.2.2 The Terminalia sericea - Combretum collinum moderately closed shrub- and bushland subassociation............................................................................. 39 6.2.3 The Terminalia sericea - Acacia mellifera short, moderately closed bushland subassociation ........................................................................................... 45 7 The Acacietea ....................................................................................................... 50 7.1 The Terminalia sericea – Acacia erioloba short, moderately closed bushland association ............................................................................................................................ 50 7.2 The Eragrostis rigidior - Urochloa brachyura tall, semi-open shrubland association of the omiramba ....................................................................................................... 54 7.3 The Acacia mellifera – Stipagrostis uniplumis tall to high moderately closed shrubland association ........................................................................................................... 57 7.3.1 The Acacia mellifera - Rhigozum brevispinosum tall, moderately closed shrubland subassociation ........................................................................................... 57 7.3.2 The Acacia mellifera – Stipagrostis uniplumis high, moderately closed shrubland subassociation ........................................................................................... 61 7.3.3 The Acacia mellifera - Catophractes alexandri tall, moderately closed shrubland subassociation ........................................................................................... 63 7.3.4 The Ziziphus mucronatha - Acacia hebeclada tall, moderately closed shrubland subassociation ........................................................................................... 66 7.4 The Enneapogon desvauxii – Acacia hebeclada tall, semi-open to moderately closed shrubland association............................................................................................ 69 7.4.1 The Eriocephalus luederitzianus – Eragrostis echinocloidea tall, semi-open shrubland subassociation ........................................................................................... 69 7.4.2 The Enneapogon desvauxii – Acacia hebeclada tall, moderately closed shrubland subassociation ........................................................................................... 72 7.5 The Acacia luederitzii - Ptycholobium biflorum short, moderately closed bushland association ........................................................................................................... 74 7.6 The Hyphaene